The subject matter disclosed herein relates to improvements in fluid flow technology with particular discussion about embodiments of a flow restrictor that address operating problems on pilot operated relief valves.
In general, relief valves are useful to allow fluid to flow out of a system or vessel in response to pressure that exceeds certain design limits. A pilot operated relief valve system (also “PORV assembly”) is a type of relief valve system that use system pressure to hold a sealing element (e.g., a piston) against a seat. The resulting seal prevents fluid from venting from the system (or vessel) through the PORV assembly during normal operating conditions (e.g., normal pressure). As the name implies, the PORV assembly also includes a pilot valve that couples with the main valve. This configuration allows the pilot valve to vent fluid from the main valve in the event of an over-pressure event. The reduction in pressure in the main valve frees the piston to move and exhaust fluid from the system. The pilot valve will close when the system pressure decreases to an appropriate level, which in turn allows the main valve to pressurize to close and seal the sealing element against the seat.
PORV assemblies and related devices will often include a flow restrictor, or related device, that is configured to condition the flow of system fluid. In many PORV assemblies, the flow restrictor is found upstream of the pilot valve. This configuration allows the flow restrictor to modify flow parameters (e.g., velocity and/or pressure) of the system fluid to allow the pilot valve to open, close, or otherwise perform according to its design requirements and/or system-level design specifications. Nominally, the flow restrictor resolves instabilities in the valve assembly that may prevent the main valve from opening at appropriate overpressure levels and, thus, increasing the risk of damage to the vessel and/or system during overpressure events.
In conventional design, flow restrictors direct the system fluid through an orifice having dimensions that impart appropriate changes to the flow parameters. This orifice typically restricts flow of the system fluid, thereby rendering flow at the outlet of the flow restrictor with flow properties that are favorable to the design of the fluid circuit and/or implementation on the PORV assembly. Some designs for flow restrictors allow an end user to adjust the orifice dimensions to change the flow properties of fluid at the outlet. This feature can alleviate instabilities that are caused by slight variations in operation that are inherent from one pilot valve to the next.